<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
		
			/*子元素的标签应该要统一*/
			/*ul .item:nth-child(3){
				border: 1px solid;
			}*/
		
		
			ul .item:nth-of-type(3){
				border: 1px solid;
			}
			/*ul p:nth-of-type(3){
				border: 1px solid;
			}
			ul div:nth-of-type(3){
				border: 1px solid;
			}
			ul li:nth-of-type(3){
				border: 1px solid;
			}*/
		</style>
	</head>
	<body>
		<ul>
			<p class="item">p1</p>
			<p class="item">p2</p>
			<p class="item">p3</p>
			<li class="item">1</li>
			<li class="item">2</li>
			<li class="item">3</li>
			<li class="item">4</li>
			<li class="item">5</li>
			<div class="item">div1</div>
			<div class="item">div2</div>
			<div class="item">div3</div>
			<li class="item">6</li>
			<li class="item">7</li>
			<li class="item">8</li>
			<li class="item">9</li>
		</ul>
	</body>
</html>
